Wind energy has been harnessed for centuries and used for a variety of useful purposes including propelling sailing ships to newly discovered continents, grinding grain, pumping water, and generating electricity. In recent times, large propeller-type horizontal axis turbines have been mounted on towers and used to turn electrical generators to provide a portion of the power for a large electrical distribution grid. Significant numbers of these wind turbines have been located in particular areas with high average wind speeds to form wind farms with considerable generating capability. Wind turbines have also been used to generate electricity in off-grid applications such as remote sites.
Wind energy is a potential substitute for at least a portion of the power generated by burning fossil fuels in conventional power plants, and use of wind energy instead of fossil fuels reduces the production of atmospheric pollution that otherwise would result from burning fossil fuels. In addition to the traditional pollutants from burning of fossil fuels, such as hydrocarbons, carbon monoxide, particulates, and acid rain, as examples, use of wind energy reduces the production of greenhouse gasses (i.e., carbon dioxide), in comparison with fossil fuels, and the contribution to the risks and potential harm associated with global warming. Further, use of wind energy reduces the need for the sacrifice of land for open pit mining and the risk to underground workers associated with underground mining of fossil fuels such as coal, or nuclear reactor fuels such as uranium, as examples. Use of wind energy instead of nuclear power also helps to avoid the risk of accidents and terrorist acts, as well as the long-term commitment of future generations associated with the production of radioactive waste.
According to the American Wind Energy Association, the U.S. Department of Energy has estimated that the wind energy potential in the U.S., for example, exceeds the total U.S. electrical consumption today. However, certain locations are far better than others for locating devices that harness wind energy, and available locations with adequate and relatively consistent wind speeds are limited. Further, state-of-the-art wind turbines usually must be spaced apart from one another by a fairly substantial distance to avoid overly impacting the flow of the wind to adjacent turbines. Consequently, the number of wind turbines that have been installed in a particular area of land has been rather limited. Thus, a need exists, or potential for benefit, to be able to improve the power production capability of a new or existing wind farm, or of a particular area of available land. Further, needs and potential for benefit exist for a wind farm that allows greater power production per area of land, more wind turbines per area of land, less interference between adjacent wind turbines, or wherein adjacent turbines improve wind speeds through each other, at least in some cases, rather than reducing wind speeds through each other.
Additionally, prior art horizontal-axis wind turbines are typically mounted on a tall tower. In addition to accessing higher wind speeds, the height of traditional wind turbines reduces or avoids risk to people, livestock, and wildlife, that may be on or near the ground. But towers are expensive to build and, at least in some cases, their height may be objectionable, for example, for obstructing a view. Thus, needs and potential for benefit exist for a wind turbine that will work well near the ground without putting people, livestock, or wildlife at excessive risk. In addition, flying birds are often killed or injured by traditional exposed wind turbines, and needs and potential for benefit exist, especially in certain locations, for wind turbines that protect birds from harm or that reduce the risk to birds inhabiting or passing through the area.
Further, due to the large size of the blades, and limitations on tip speeds, for example, prior art horizontal-axis wind turbines typically require a speed increaser between the turbine and the generator. Speed increasers have equipment costs, frictional losses, maintenance requirements, and risks of breakdown associated with them. Large blades are also an expensive component of existing wind turbines, and require high towers, which are another expensive component. Thus, needs and potential for benefit exist for a wind turbine in which the propeller turns at a higher speed so that a speed increaser is not required, need not increase the speed as much (e.g., proportionally), or need not handle as much torque (e.g., be as large), particularly while meeting other needs and potential areas for benefit. Needs and potential for benefit also exist for a wind turbine having smaller blades.
Still further, wind energy production has been increasing dramatically around the world in recent years. In response to the demand, installed costs for horizontal-axis wind turbines have increased on a per KWH basis as the best sites have been utilized, for example. In addition, increasing demand on limited wind turbine production capacity has resulted in both increases in cost and delays in obtaining specialized wind turbine equipment. As a result, needs and potential for benefit exist for alternative configurations of wind turbines that utilize different construction methodologies, that require different construction facilities, that compliment rather than competing directly with existing horizontal-axis wind turbine designs, and that are competitive with prior art technology on a cost per KWH basis, delivery time basis, or both. Furthermore, needs and potential for benefit exist for alternative configurations of wind turbines that facilitate faster or less expensive manufacturing and implementation of wind energy production capability on a worldwide basis.
Even further, structures have been proposed for focusing wind onto a turbine. U.S. Pat. No. 6,710,468 (Marreo O'Shanahan) concerns a wind-channeling conduit with a rotor within a narrowing in the conduit. U.S. Pat. No. 1,471,095 (Bonetto) shows two funnels 16 and 17 between which are blades 27 which turn a shaft 29. And U.S. Pat. No. 3,883,750 (Uzzell) shows a fan within a venturi, while U.S. Pat. No. 4,021,135 (Pedersen) shows a rotor 14 within a cowling 17. However, needs and potential for benefit exist for a venturi that has a shape that further reduces losses as air passes through the venturi. In addition, vertical axis and Savonius-type rotors or wind turbines have been proposed in the prior art. Bonetto, U.S. Pat. No. 4,474,529 (Kinsey), U.S. Pat. Nos. 5,332,354, and 5,852,331 show various vertical axis wind turbines. Further, U.S. Pat. No. 6,538,340 (Elder) contemplates use of a sandwich material for construction of wind turbine systems. Potential for improvement exists in these and other areas that may be apparent to a person of skill in the art having studied this document.